Process for producing epsilon-caprolactam

ABSTRACT

Epsilon-caprolactam is prepared without the formation of byproduct ammonium sulfate by contacting at least one of Epsilon caprolactone or a C1-4 lower alkyl ester of Epsilon hydroxycaproic acid, hydrogen and ammonia in the vapor phase at 200* to 320*C. with a solid catalyst comprising (A) at least one oxide selected from titanium dioxide, alumina, aluminasilica and silica, and (B) metallic copper. Optionally the catalyst contains metallic nickel and/or chromium sesquioxide.

United States Patent Fujita et al.

PROCESS FOR PRODUCING EPSILON-CAPROLACTAM Inventors: Yutaka Fujita;Tatsuyuki Naruchi;

Eishin'Yoshisato, all of Iwakuni, Japan Assignee: Teijin Limited, Osaka,Japan Filed: Mar. 5, 1971 Appl. No.: 121,550

Foreign Application Priority Data Mar. 9, 1970 Japan 45-20008 Apr. 10,1970 Japan 45-31012 Apr. 15, 1970 Japan....,. 45-32074 Oct 12, 1970Japan 45-88773 Oct. 15, 1970 Japan 45-90060 Nov. 19, 1970 Japan45-102166 Dec. 28, 1970 Japan 45-123958 US. Cl 260/2393 A; 252/454;252/455 R;

252/476; 252/474; 252/467 Int. Cl C07d 41/06 Field of Search 260/2393 A[56] References Cited UNITED STATES PATENTS 2,817,646 12/1957 Payne260/2393 A 3,317,516 5/1967 Mifune et a1. 260/2393 A 3,317,517 5/1967Mifune et a1. 260/2393 A FOREIGN PATENTS OR APPLICATIONS 1,506,87411/1967 France 260/2393 A Primary Examiner-I-Ienry R. Jiles AssistantExaminer-Robert T. Bond Attorney, Agent, or Firm-Sherman & Shalloway 5 7ABSTRACT Epsilon-caprolactam is prepared without the formation ofby-product ammonium sulfate by contacting at least one of e-caprolactoneor a C H lower alkyl ester of e-hydroxycaproic acid, hydrogen andammonia in the vapor phase at 200 to 320C. with a solid catalystcomprising (A) at least one oxide selected from titanium dioxide,alumina, aluminasilica and silica, and (B) metallic copper. Optionallythe catalyst contains metallic nickel and/or chromium sesquioxide.

8 Claims, No Drawings PROCESS FOR PRODUCING EPSILON-CAPROLACTAM Thisinvention relates to a process for producing e-caprolactam, and moreparticularly to a process for producing e-caprolactam by contactinge-caprolactone, hydrogen and ammonia with a catalyst in the vapor phase.

As is well know, e-caprolactam is commercially produced in largequantities as a material for nylon 6, and is a very important compound.Various methods have previously been proposed for the production ofe-caprolactam. Many of the commercial methods, however, yield largequantities of by-product ammonium sulfate. Formerly, ammonium sulfatewas regarded as very valuable for use in chemical fertilizers, butbecauseit renders the soil extremely acidic, it has gradually beensuperseded by urea or other compounds. Thus, the value of ammoniumsulfate as a fertilizer has been greatly reduced, and the disposal ofthe by-product ammonium sulfate constitutes a great setback.Accordingly, the cost of production cannot be reduced with the methodsof producing e-caprolactam in which ammonium sulfate is produced ingreat quantities as a byproduct. The difficulty of disposing theby-product ammonium sulfate also prevents the construction of largescaleequipment. For these reasons, there is a strong demand for thedevelopment of a commercial method which is free from the formation ofby-product ammonium sulfate.

Methods free from the formation of by-product ammonium sulfate have infact been proposed, as is seen from US. Pat. No. 3,000,880 whichdiscloses a'process for producing e-caprolactam by heatinge-caprolactone in an aqueous solution of ammonia. These methods,however, require extremely high temperatures and pressures, and are notcommercially feasible. Moreover, the products obtained by these methodsdo not prove satisfactory.

Accordingly, an object of the present invention is to provide a processfor producing e-caprolactam in one step by the vapor phase catalyticreaction of e-caprolactone or C -C alkyl esters of e-hydroxycaproicacid, which process does not yield by-product ammonium sulfate.

Another object of the invention is to provide a process for producinge-caprolactam at high conversions and selectivities by the vapor phasecatalytic reaction at relatively low temperatures and pressures using asreactants e-caprolactone or said ester C -C alkyl esters ofe-hydroxycaproic acid, hydrogen, ammonia, and if desired, water, whichreactants are available at very low cost.

Still another object of the invention is to provide a novel catalystsystem that can be used in the above vapor phase catalytic reaction.

Other objects and advantages of the invention will become apparent fromthe following description.

According to the present invention, e-caprolactam is produced at highconversion and selectivity by contacing e-caprolactone or at least one C-C alkyl ester of ehydroxycaproic acid, hydrogen and ammonia with asolid catalyst comprising (a) at least one oxide selected from the groupconsisting of titanium dioxide, alumina, alumina-silica and silica and(b) metallic copper, in the vapor phase at 200C. to 320C.

The invention will be described below in greater detail.

STARTING MATERIALS In the present invention, e-caprolactone or at leastone lower alkyl ester having 1 to 4 carbon atoms of e-hydroxycaproicacid or a mixture of two or more of these esters are used as thestarting materials. When the ester is used as the starting material, analcohol, one of the constituents of the ester, is formed as a by-productof the reaction according to the invention, and an extra step ofrecovering the alcohol is needed. It is most advantageous therefore touse e-caprolactone as the starting material.

Preferred esters of e-hydroxycaproic acid are those having 1 to 4 carbonatoms, such as methyl, ethyl, propyl and butyl esters. With anincreasing number of carbon atoms, the esters have a higher boilingpoint, and make it more difficult to operate the vapor phase reaction ofthe invention. Sometimes, the operation needs to be carried out atreduced pressure, and both the efficiency of the equipment and the rateof forming the lactam are reduced. Accordingly, the methyl or ethylester is especially suitable.

The e-caprolactone may be produced by any method. For example, it can beprepared in good yields by a method wherein e-hydroxycaproic acid or itsester is distilled by heating in the presence of boric acid (French Pat.No. 1,474,098), or a method wherein cyclohexanone is oxidized with aperoxide (US Pat. NO. 3,064,008 and British Pat. No. 841,839).

The C -C alkyl esters of e-hydroxycaproic acid used in the invention canbe readily prepared, for example, by esterifying hydroxycaproic acid ore-caprolactone with lower alcohols having 1 to 4 carbon atoms.

e-Hydroxycaproic acid can be produced in high yields, for example, byair oxidation of cyclohexane or a mixture of it with cyclohexanone orcyclohexanol in the absence of a solvent (for example, British Pat. No.935,029 and French Pat. No. 1,275,952).

The present invention has the great advantage that e-caprolactam can beproduced in high yields without the formation of by-product ammoniumsulfate by using the e-caprolactone or C -C alkyl esters ofe-hydroxycaproic acid which are commercially available at relatively lowcost.

CATALYST As previously stated, asolid catalyst basically comprising thefollowing two components:

A. at least one oxide selected from the group consisting of titaniumdioxide (TiO alumina (Al O alumina-silica (Al O SiO and silica (SiO (tobe referred to as component A), and

B. metallic copper (to be referred to as component B) is used.

Investigation has revealed that the aforesaid oxide (component A) andmetallic copper (component B), when used individually, shown little orno catalytic activity in the reaction for producing e-caprolactamaccording to the present invention, but when combined with each other toform the catalyst system of the invention, exhibit very strong catalyticactivity. The preferred catalyst system to be used in the inventioncomprises 100 parts by weight of the oxide (component A) and 0.5 to 200parts by weight, preferably 5 to 100 parts by weight, more preferably 10to parts by weight, of metallic copper (component B). If the content ofmetallic copper is outside the range specified above, the yield ofe-caprolactam as the desired product is reduced unfavorably.

The catalyst to be used in the invention should preferably be a mixturein which the metallic copper comes in intimate contact with particlesand/or agglomerated particles of the oxide having an average particlediameter of 5 to 100 microns, preferably to 50 microns, especially onein which the metallic copper is deposited on the surfaces of theparticles or agglomerated particles of the oxide. The average particlediameter used herein refers to an average diameter calcualted accordingto the formula to be described on the basis of the sedimentation speedwhich is measured by the sedimentation method widely used, such as thepipette method, sedimentation pipe method, sedimentation balance method,or centrifugal sedimentation method. It is preferred that at least 50 byweight, especially at least 80 by weight of the entire particles and/oragglomerated particles of the oxide should have a particle diameter inthe range of 5 to 100 microns, preferably in the range of 10 to 50microns, and moreover, the average particle diameter of the entireparticles should be within this range. Generally, those having a narrowsize distribution are preferred.

The average particle diameter of the particles and/or agglomeratedparticles of the oxide as component A is determined by the followingStokes equation.

1 1/2 h l/2 De EMF/ lu] t wherein De is an average particle diameter incentimeters, is the viscosity coefficient of a medium in g/cm.sec., ppisthe density of particles in g/cm p is the density of the medium in g/cmg is the acceleration of gravity (980 cm/sec h is the distance overwhich the particles sediment in centimeters, and

t is the time in seconds needed for sedimentation over the distance h.

The relation between the sedimentation velocity and the particlediameter of anatase-type titanium dioxide (TiO (density 3.84) in purewater was determined according to the foregoing equation. Thesedimentation velocity v is obtained by coverting h/t to thesedimentation distance (cm/min.) per minute. The results are shown inthe following Table.

Particle diameter Thus, the average particle size of titanium dioxidecan be readily determined by measuring the precipitating rate oftitanium dioxide in pure water. The average particle diameter of otheroxides can also be deter- Al O /SiO ratio of 1 or more, and ordinarysilica gel is used as the silica.

The preparation of the solid catalyst of the present inventionconsisting basically of the oxide (component A) and metallic copper(component B) is effected, for example, by dispersing the oxide in anaqueous solution of a copper compound or an aqueous suspension of thecopper compound, precipitating the copper compound from the solutionwhen the aqueous solution of the copper compound is used, separating amixture of solid copper compound and the oxide from the aqueous medium,calcining the mixture at a temperature sufficient to convert the coppercompound to copper oxide but preferably not to sinter the resultingcopper oxide, for example 200 to 800C., preferably 250 to 600C. for aproper period of time (calcining step), and thereafter, reducing themixture until at least the surface of the copper oxide is substantiallyconverted to metallic copper (reducing step).

The reduction of copper oxide is effected by using a suitable reducingagent, preferably hydrogen at to 350C, preferably 170 to 270C. Thereduction reaction may be continued until the generation of water by thereduction of copper oxide is substantially completed. Since the reactionis generally exothermic, it is desirable to exercise care so that theresulting metallic copper will not be sintered.

A mixture of copper oxide formed by the calcining step and the oxide ascomponent A, if desired, may be fabricated to suitable size prior to thereducing step. Such fabrication is not always necessary since thecatalyst of the present invention can be used as a fluidized bed as willbe described later.

In the preparation of the catalyst of the present invention, anywater-soluble or water-insoluble copper compounds can be used which canbe converted to copper oxide in the aforementioned calcining step.

(step of producing copper oxide). Examples of the water-soluble coppercompound include water-soluble or water-insoluble inorganic and organicacid salts of copper, such as inorganic acid salts of copper including,for example, copper nitrate, sulfate, hydrochloride or hydrobromide, andorganic acid salts of copper including copper acetate, benzenesulfonateor toluenesulfonate; water-soluble copper complexes such aswater-soluble copper ammine complex; and other water-soluble coppercomplex salts. The deposition or sedimentation on the oxide particles ascomponent A of such water-soluble copper compound by precipitating itfrom its aqueous solution can be effected by a suitable method such asby heating and concentrating an aqueous solution of the water-solublecopper compound, and/or adding alkali. The aforementioned Water-solublecopper compounds may be directly converted to copper oxide in thecalcining step, or a copper compound formed by the reaction of thecopper compounds with the alkali mentioned above may be convertible tocopper oxide in the calcining step. As the alkali to be used forprecipitating a copper compound from an aqueous solution of thewatersoluble copper compound, various compounds are used such as sodiumcarbonate, potassium carbonate, sodium hydroxide, potassium hydroxide,aqueous ammonia, am monium carbonate, sodium bicarbonate, potassiumbicarbonate, and ammonium bicarbonate. At the time of adding the alkali,an aqueous solution of the copper compound may be heated properly. Whenthe copper compound is precipitated by adding alkali, it is preferred toremove the wter-soluble salt produced by addition of alkali by asuitable method such as wasing prior to the calcining step.

Those water-insoluble copper compounds mentioned above which can beconverted to copper oxide in the calcining step are, for example, copperhydroxide, hydrated copper oxide, copper carbonate, basic coppercarbonate, and copper oxalate. When the waterinsoluble copper compoundis used, it is mixed in a powder form or an aqueous suspension with theoxide (component A), and if desired after separating water, the mixtureis calcined and reduced as mentioned above.

As described above, the preparation of the catalyst of the presentinvention is performed by depositing or sedimenting the copper compoundon the surfaces of particles or agglomerated particles of the oxide(component A), calcining them under the proper temperature and timeconditions mentioned above to convert the copper compound to copperoxide, and preferably reducing the largest possible area of the copperoxide to convert at least the surface of the copper oxide to metalliccopper (component B). It is convenient that the average particlediameter of the oxide (component A) be adjusted to the aforementionedrange.

Investigation has revealed that a catalyst of long life and highactivity can be obtained by adding small amounts of metallic nickeland/or chromium sesquioxide (Cr O (to be referred to as component C) tothe catalyst of the present invention.

Barium oxide (BaO) and manganese oxide (MnO are compounds well known asa sintering inhibition agent for a copper catalyst, but it has beenfound that the addition of a small amount of barium oxide or manganeseoxide to the catalyst composed of the two components A and B givevirtially no advantage. Various catalysts have also been prepared bycoprecipitating a small amount of cobalt metal (Co), calcium oxide(CaO), zinc oxide (ZnO), magnesium oxide (MgO), aluminum oxide (A1 0 oriron oxide (Fe O and the aforesaid water-soluble copper compound on theoxide particles (component A), and subjecting them to the calcining andreducing steps, with studying of their activities, lives, etc. It hasbeen found that these third components have no particular merit. Theinvestigation led to the discovery that all of these third componentsincluding the aforementioned barium oxide and manganese oxide, whenadded in an amount of 0.02 or more in terms of the atomic ratio based oncopper (Cu), commonly reduce the activity of the resulting catalyst, andthat if the content is less than 0.02, especially less than 0.01 thethird component neither gives merit or demerit (the composition of thethird component is expressed as the typical chemical composition in theresulting catalyst after the calcining and reducing steps).

However, the aforementioned metallic nickel and/or chromium sesquioxide(component C) apparently behave differently from the third componentsmentioned. By incorporating small amounts of such component C in thecomponents A and B, a highly active catalyst is obtained having a longercatalyst life than a catalyst obtained from the two components A and Balone.

The amount of metallic nickel and/or chromium sesquioxide (component C)is such that the sum of the amounts of metallic copper (component B) andmetallic nickel and/or chromium sesquioxide (component C) is 0.5 to 200parts by weight, preferably 5 to 100 parts by weight, more preferably 10to by weight, per parts by weight of at least one oxide (component A)selected from titanium dioxide, alumina, alumina-silica and silica, andthat component C is 0.001 to 1 atom, particularly 0.005 to 0.25 atom,calculated as the nickel (Ni) and/or chromium (Cr) per atom of copper.

The preparation of the catalyst of the invention containing thecomponent C is performed by forming a mixed aqueous solution of awater-soluble copper compound and a water soluble nickel compound and/orwater-soluble chromium compound, heating and concentrating the mixedaqueous solution or adding an alkali to the mixed aqueous solution tothereby precipitate the nickel compound and/or chromium compound as awaterinsoluble compound together with the copper compound, thereafterseparating them together with component A from water, and calcining andreducing these compounds to convert the copper compound to metalliccopper and simultaneously convert the nickel compound and/or chromiumcompound to metallic nickel and/or chromium sesquioxide (component C).Any nickel compounds and/or chromium compounds can be used which can becoverted to metallic nickel and/or chromium sesquioxide by the calciningand reducing steps, and water-insoluble compounds of nickel and/orchromium can also be used.

Of the methods of preparing the catalyst of the invention, the so-calledsedimentation method is preferred in which the oxide as component A issuspended in an aqueous solution of a water-soluble copper compound, oran aqueous solution of the copper compound together with a water-solublenickel compound and/or water-soluble chromium compound, and an alkali isadded to precipitate the copper compound or the copper compound and thenickel compound and/or chromium compound.

ln the production of e-caprolactam in accordance with the process of thepresent invention, the amount of hydrogen used is desirably 5 to 70moles, preferably 10 to 50 moles per mole of the e-caprolactone and/ore-hydroxycaproic acid lower alkyl ester. Amounts below this range causea decrease in the selectivity to e-caprolactam, and amounts in excess ofthis range do not increase the selectivity. The suitable amount ofammonia is l to 50 moles, preferably 2 to 25 moles per mole of thee-caprolactone and/or lower alkyl ester of e-hydroxycaproic acid.Amounts outside this range result in the reduction in the selectivity ofe-caprolactam.

In addition to the amounts of hydrogen and ammonia specified as againstthe amount of e-caprolactone and- /or lower alkyl ester ofe-hydroxycaproic acid, the amount of hydrogen, per mole of ammonia, isspecified as 0.2 to 30 moles, preferably 0.5 to 15 moles, so thate-caprolactam can be obtained at the most preferable selectivity. If theratio of ammonia to hydrogen falls outside this range, the selectivityof e-caprolactam is decreased.

According to the present invention, e-caprolactam is produced at a highselectivity by contacting a gaseous mixture of e-caprolactone and/orlower alkyl ester of e-hydroxycaproic acid, hydrogen and ammonia of theabove-specified amounts with the catalyst obtained in the mannerspecified above. If water is allowed to be present in the reactionsystem, the side-reactions are inhibited, and e-caprolactam can beproduced at a high selectivity. Furthermore, in the presence of water,the

life of the catalyst is prolonged. The amount of water" used for thispurpose is to 50 moles, preferably to 30 moles, per mole ofe-caprolactone and/or lower alkyl ester of e-hydroxycaproic acid.Amounts above 50 moles are not commercially desirable, since the spacetime yield of e-caprolactam is decreased.

The reaction temperature in the process of the invention is determinedaccording to such factors as the activity of the catalyst used. Thepreferred temperature is 200 to 320C., especially 220 to 3 C.Attemperatures below 220C., particularly below 200C, the reaction to forme-caprolactam is not sufficiently performed, and a high degree ofreduction in pressure is needed in order to maintain the reaction systemvaporous. In addition, the space time yield of e-caprolactam is reduced.On the other hand, the occurrence of sidereactions is vigorousattemperatures above 310C., especially above 320C., and the life of thecatalyst be comes short.

The reaction pressure is dependent upon the reaction temperature, butusually ranges from 0.01 to 2 atmospheres, preferably from 0.1 to 1.2atmospheres.

The space velocity is determined by such factors as the reactiontemperature, reaction pressure or life of the catalyst. It is usually inthe range of 70'to 3600 liters/hr. liter, preferably 200 to 900liters/hr. liter. The space velocity is the volume velocity (liter/hr.)of gas calculated per catalyst filled volume (liter) in a normalcondition.

Any apparatus can be used in the practice of the process of the presentinvention which is usually employed in the vapor phase catalyticreaction. The contacting of the reactants with the catalyst may beeffected in a fixed bed, fluidized bed or moving bed.

The reaction gaseous mixture discharged from the reaction vessel iscooled and condensed to yield a light yellow liquid matter. This mattercontains unreacted substances, intermediates and/or by-products such ase-caprolactone, e-hydroxycaproamide, or cyclopentanone, besidese-caprolactam as principal product, and thereafter, e-caprolactam isseparated and recovered from the condensed liquid.

Where e-caprolactone is used as the material, a greater part of gas notcondensed consists of hydrogen and ammonia. When the lower alkyl esterof e-hydroxycaproic acid is used, an alcohol corresponding to the esteris contained together with hydrogen and ammonia. If the gas contains thealcohol, the alcohol is separated and hydrogen and ammonia are recycledwith or without separation.

In the reaction of the present invention as mentioned above,e-hydroxycaproamide is formed as a by-product together withe-caprolactam. This can be converted readily to e-caprolactone by thebelow-mentioned method or to -caprolactone by other methods.

e-Hydroxycaproamide is saponified with sodium hydroxide or potassiumhydroxide to convert it to the alkali salt of e-hydroxycaproic acid. Thealkali salt is acidified with a strong acid such as sulfuric acid orbydrochloric acid to form free e-hydroxycaproic acid, which is cyclizedby heating to form e-caprolactone which can be used as the startingmaterial of the present invention. In the heat-cyclization, NaOH,divalent metallic halides, KCN, MgO, ZnO, CdCO ortho-. oric acid,metaboric acid, boric anhydride and B 03 are preferably used'ascatalysts (French Pat. Nos. 1411213, 1474903, and 1474098).

On the other hand, e-hydroxycaproamide'can be converted to e-caprolactamby heating it in water at 3 0047 5C. without conversion toe-caprolactone (U.S. Pat/No. 3,000,879).

I Accordingly, 'vs-hydroxycaproamide formed by the process of theinvention can be readily converted to e-caprolactone or e-caprolactam,and therefore the formation of it in a small amount does not constituteany particular setback.

g The catalytic activity of various solid acids, such as thorium oxide(ThO acid clay, kaolin, bentonite, diatomaceous earth, zirconiumsilicate, and zinc borate,

either alone or in combination with metallic copper (component B), inthe vapor phase catalytic reaction of e-caprolactone or a lower alkylester of e-hydroxycaproic acid, hydrogen and ammonia has been studied.In

all instances, the selectivity of e-caprolactam has been found to beless than 50 and these solid acids did not exhibit a catalyticperformance that is commercially feasible. Zinc oxide or magnesium oxidegave only unsatisfactoryresults as inthe case of these solid acids.

Unexpectedly, the use of the catalyst of the invention which is composedof the components A and B or the components A, B and C described abovemakes it possible, quite different from the above-mentioned solid.acids, to produce ecaprolactam at very superior con-. .version andselectivity.

As will be mentioned below, the catalyst of the present invention can beactivated by a simple method, and

repeatedly used for further reaction. In this respect also, the processof the present invention is very superior to the conventional processes.

REGENERATION OF CATALYST -so regenerated can be directly used .for thereaction,

but becomes more effective if hydrogen is passed through it at l70-350C.prior to use.

The oxidation-reduction (ii) is performed by contacting the catalystwith molecular oxygen-containing gas at l00800C., preferably l50500C.,for 20 minutes to 20 hours, and thencontacting it with hydrogen gas atl-350C., preferably l70-270C. In this extent such that the activitybecomes substantially the same as the initial activity.

The activity of the catalyst can be readily restored by these catalystregenerating methods (i) and (ii), and therefore, the catalyst of thepresent invention is commercially very superior.

The invention will now be described in greater detail by the followingExamples which are not intended in any way to limit the invention.

EXAMPLE 1 Copper nitrate trihydrate (121.6 g) wasdissolved in one literof water, and 160 g of the powders of titanium oxide were suspended inthis aqueous solution. With good stirring, an aqueous 10% solution ofsodium carbonate was gradually added dropwise to the solution at roomtemperature for 30 minutes to adjust the pH of the solution to 7.5.Stirring was continued for a further 1 hour, and the solution wasallowed to stand overnight. The solution was then filtered, and thefiltrate was thoroughly washed with water, and then dried at 90100C. Theresulting powders were carefully decomposed by heat in a stainless steelcontainer with good stirring. The composition of the resulting calcinedproduct corresponded to 20 wt. CuO and 80 wt. TiO and the weight ratioof Cu/TiO and the weight ratio of Cu/TiO after reduction with hydrogencorresponded to 0.20. This powdery calcined product was kneaded withwater, dried, and pulverized. Particles having a size of 9 12 mesh werecollected.

The reaction apparatus consisted of a preheating pipe having a length of500 mm and an inner diameter of 24 mm and a reaction pipe having alength of 600 mm. The preheating pipe was placed at the upper portionand the reaction pipe at the lower portion, both inclined at 30 and bothends were connected. The preheating pipe was packed with 180 cc of glassballs having a diameter of 3 mm. At about the center of the preheatingpipe an opening was provided through which water was to be added and ata position about A of the entire length from the upper end, an openingfor feeding the materials was provided. The reaction pipe was packed,beginning with the connecting portion with the preheating pipe, with 120cc of glass balls each having a diameter of 3 mm, 80 cc (68 g) of thecatalyst prepared above, and 20 cc of glass balls, in the order men-.tioned. A thermometer was set up about the center of the catalyst layer.A band heater was wound around the preheating pipe and the reactionpipe, and an asbestos band was wound thereon.

Nitrogen gas was introduced from the upper end of the preheating pipe,and after thorough replacement of the inside atmosphere by nitrogen gas,a gaseous mixture of 0.02 0.04 liter/min. of hydrogen gas and 0.50liter/min. of nitrogen gas was passed through the pipe for 5 hours at170250C., and then 0.20 liter/min. of hydrogen gas was passed therethrough for 2 hours at 250C. Thereafter, the temperature of thepreheating pipe and that of the reaction pipe were set at 250C.

Hydrogen gas was introduced at a flow rate of 0.23 liter per minute fromthe upper end of the preheating pipe, and while introducing ammonia gasat a flow rate of 0.05 liter per minute (calculated as these gases in anormal condition) from the upper end of the reaction pipe,e-caprolactone was added dropwise from the material feed opening at arate of 0.051 g/min. (0.010 liter/min. calculated as the material in anormal condition). Thus, over a period of 3 hours, 9.2 g ofe-caprolactone were added dropwise, and for additional 3 hours at thesame temperature, the hydrogen gas, ammonia gas and water wereintroduced at the same rates. The reaction product collected in areceiver cooled with dry ice-methanol was extracted five times with anequal amount of chloroform. The chloroform solution was concentrated,and quantitatively analyzed by gaschromatography. It was found that 7.1g of e-caprolactam and 1.07 g of e-caprolactone were obtained.

The residual aqueous phase resulting from the ch10 roform extraction, onaddition of sodium hydroxide, was refluxed for 3 hours, and acidifiedwith hydrochloric acid, followed by continuous extraction with ether for5 hours. The ether solution was treated with diazomethane to yield amethyl ester, which was then quantitatively analyzed bygaschromatography. lt was found that 0.16 g of methyl e-hydroxycaproatewas yielded. The aqueous phase remaining after the chloroform extractioncontained e-hydroxycaproic acid amide and a small amount of ammoniume-hydroxycaproate. It is assumed that these compounds were formed by thereaction unreacted e-caprolactone in the receiver after termination ofthe reaction for form e-caprolactam, or during the treatment of thereaction product. They were quantitatively analyzed as methyle-hydroxycaproate, and in calculation, dealt with as unreactede-caprolactone.

The space velocity of the foregoing reaction was 368 liters/hr. liter.

(The amounts of the e-hydroxycaproamide and ammonium e-hydroxycaproateincrease or decrease according to the time needed until the treatment ofthe reaction product, the temperature and state of the reaction product,or the method of chloroform extraction, and their proportions withrespect to unreacted e-caprolactone differ. The results, of the reactioncan be precisely compared by treating them as mentioned above, andquantitatively analyzing e-hydroxycaproamide and ammoniume-hydroxycaproate as methyl e-hydroxycaproate, and dealing with it asunreacted e-caprolactone.)

The yield of e-caprolactam was 78%, the conversion of e-caprolactone was87%, and the selectivity of e-caprolactam was 90%. The yield ofe-caprolactam, the conversion of e-caprolactone and the selectivity ofe-caprolactam were calculated according to the following equations.(This will apply to all other Examples and Controls.)

Moles of e-caprolactam yielded Moles of e-caprolactone fed [Moles ofecaprolactone reacted moles of e-caprolactone moles of e-caprolactonerecovered moles of methyl e-hydroxycaproate recovered] EXAMPLES 2 TO 11AND CONTROLS 1 AND 2 Examples 2 to 11 show the relation of the weightratio of copper or copper and nickel to the titanium di oxide, to theresults of the reaction.

A catalyst composed of titanium dioxide and copper was prepared in thesame manner as in Example 1. A catalyst consisting of titanium dioxide,copper and nickel was prepared in the same way as in Example 1 using amixed aqueous solution of copper nitrate and nickel nitratecorresponding to the composition of the catalyst instead of the aqueouscopper nitrate solution.

In Example 1 1, the catalyst used was prepared in the same way as setforth in Example 96 to be described by suspending basic copper carbonateand titanium dioxide in water, and filtering the suspension.

Using e'caprolactone (LON for short in the tables to be given) as astarting material, the process of the invention was performed in thesame way as set forth in Example 1.

Controls 1 and 2 show that titanium dioxide or metallic copper alonehardly exhibit a catalytic activity.

The catalyst used in Control 1 was prepared by kneading the powders oftitanium dioxide with water, drying the kneaded product, pulverizing thedried product, and collecting particles having a size of 9 to 12 mesh.

The catalyst used in Control 2 was prepared by adding an aqueoussolution of sodium carbonate dropwise to an aqueous solution of coppernitrate to precipitate basic copper carbonate, allowing it to standovernight, washing the precipitate with water, filtering and drying it,calcining the powdery basic copper carbonate with stirring in astainless steel vessel to form copper oxide, shaping it into tablets,pulverizing them, and collecting particles having a size of 9 to 12mesh.

In Controls, the procedure of Example 1 was exactly followed usinge-caprolactone as a starting material. The results obtained are in Tablel.

The titanium dioxide used in all of the Examples and Controls was of theanatase type.

liters of an aqueous solution. To the aqueous solution 280 g of a powderof titanium dioxide (anatase type) were added, and the solution wasstirred for 20 minutes to form a dispersion. The size distribution oftitanium dioxide in an aqueous suspension of titanium dioxide wasseparately determined by the sedimentation tube method, and found to besuch that particles having a size of less than 28y. were 4%, particleshaving a particle size of 28 to 35; were 90%, and particles having asize above 35,u were 6%.

An aqueous solution of sodium carbonate having a concentration of 1.0mol/liter was added dropwise at room temperature for about 30 minuteswhile stirring the aqueous suspension to adjust the pH of the solutionto 9.5. After continued stirring for additional 30 minutes, the solutionwas allowed to stand overnight. The resulting precipitate was washedwith water by decan tation, filtered, and dried at 90 to l 10C. Thepowders obtained were calcined carefully in a stainless steel vesselwith good stirring. The calcined product consisted of 70.0% by weight oftitanium dioxide, 28.6% by weight of copper oxide, and 1.4% by weight ofnickel oxide. The weight ratio of copper and nickel to titanium dioxideafter reduction with hydrogen was 0.34:1, and the atomic ratio of nickelto copper was 0.0521. The powdery calcined product was kneaded withwater, dried and pulverized, and particles having a size of 9 to 12 meshcollected.

The catalysts used in Examples 12 to 13 and 14 to 19 were prepared inthe same way as set forth in Example 14 using the same titanium dioxideas used in Example 14.

In each of Examples 12 to 19, the catalyst was packed into the samereaction apparatus as used in Example 1, and reduced with hydrogen at250C. or below (Examples 12 to 14), 300C. or below (Exam-, ples 15 and16), and 350C. or below (Examples 17 to 19), and in the same way as setforth in Example 1, e-caprolactone was reacted together with hydrogen,ammonia and water. After stopping the addition of e-caprolactone,hydrogen, ammonia and water were introduced for an additional two hoursat the same temperature at the same flow rates. The reaction productcollected in a receiver cooled with dry ice methanol Table 1 Compositionof catalyst Reaction conditions Results of reaction Reaction temperature Cu+Ni/TiO (wt. ratio) Ni/Cu (atomic ratio) Space velocity (l/hr.l

Runs

H,j LON (molar ratio) NH LON (molar ratio) H O/ LON (molar ratio) YieldSelectivity Conversion TiO alone Cu alone EXAMPLES 12 TO 19 TheseExamples show the relation of the nickelcopper ratio in the catalystcomposed of titanium dioxide, copper and nickel, to the results of thereaction.

The catalyst of Example 14 was prepared as follows:

Copper nitrate trihydrate (346 g) and 22 g of nickel nitrate hexahydratewere dissolved in water to form 3 The ether solution was converted to amethyl ester by treatment with diazomethane, and then methyle-hydroxycaproate was quantitatively analyzed by gaschromatography.

composition as indicated in Table 3 below.

Using the catlyst so obtained, the process of the present invention wasperformed by using e-caprolactam (LON for short) or methyle-hydroxycaproate (MHC The results are shown in Table 2. 5 for short) asa starting material.

- Table 2 Catalyst composition Reaction condition Results of reactionExample Ni/Cu Reaction S ace H /LON NH /LON l-hO/LON Yield Conver-Selec- N Cu-l-Ni/TiO; (atomic temp. ve ocity (molar (molar (molar siontivity (wt.ratio) ratio (C) (l/hr.l) ratio) ratio) ratio) l2 0.34 0.001260 368 23 5 20 84 95 88 [3 0.34 0.010 260 368 23 5 20 85 97 88 14 0.340.052 260 368 23 5 20 84 96 87 15 0.34 0.20 260 368 l8 I 20 69 97 71 160.34 0.2 260 368 20 8 20 71 98 73 17 0.33 1.0 260 368 23 20 51 97 53 I80.33 1.0 260 368 20 8 20 55 96 57 19 0.33 L0 260 368 l8 20 56 96 58Table 3 Catalyst composition Reaction conditions Results of reactionCu-lCr O Cr/Cu Reaction Example Starting Space HJLON NH ILON H O/LONYield Conver- Selec- No. Material T10 temperavelocity (molar (molar(molar sion tivity (wt. (atomic ture (l/hr.l) ratio) ratio) ratio)ratio) ratio) (C) 20 LON 0.34 0.01 260 368 20 8 20 86 98 89 2| MHC 0.34260 368 20 8 20 82 97 85 22 LON 0.35 0.05 260 368 20 8 20 85 98 87 23MHC 0.35 260 368 20 8 20 83 97 86 24 LON 0.35 0.10 260 368 20 8 20 86 9987 25 MHC 0.35 260 368 20 8 20 83 99 84 26 LON 0.35 0.20 260 368 20 8 2085 98 86 27 MHC 0.35 260 368 20 8 20 82 98 84 28 LON 0.37 0.50 260 36820 8 20 78 96 81 EXAMPLES 20 TO 28 These Examples show the relation ofthe chromium oxide to copper ratio in the catalyst composed of titaniumdioxide, copper and chromium oxide, to the results of the reaction.

The catalyst used in Example 24 was prepared as follows:

Copper nitrate trihydrate (235.0 g) and 43.2 g of chromium nitratenonahydrate were dissolved in water to form 2.5 liters of an aqueoussolution. Two hundred grams of titanium dioxide powder were added to theaqueous solution, and the solution stirred for 30 minutes.

With stirring of the aqueous suspension, an aqueous solution of sodiumcarbonate having a concentration of 1.0 mol/liter was added dropwise atroom temperature over 30 minutes to adjust the pH of the solution to9.5. After continued stirring for an additional 30 minutes, the solutionwas allowed to stand overnight. The resulting precipitate was washedwith water, filtered, and then dried at 90 to 110C. The powder wascalcined with good stirring in a stainless steel vessel. The calcinedproduct had a composition of 70.] wt titanium dioxide, 27.0 wt. copperoxide, and 2.9 wt. chromium oxide. After reduction with hydrogen, theweight ratio of copper and chromium oxide to titanium dioxide was0.35:1, and the atomic ratio of chromium to copper was 0.1:1.

The powdery calcined product was kneaded with water, dried, andpulverized, and particles having a size of 9 to 12 mesh were collected.

The catalyst used in Examples 20 to 23 and 25 to 28 was prepared in thesame manner as in the preparation of the catalyst used in Example 24 buthad a different EXAMPLES 29 TO 36 These Examples show the results of theprocess of the invention carried out using silica gel, alumina-silica oralumina, a catalyst composed of copper and nickel, or a catalystcomposed of copper and chromium oxide.

The catalyst used in Example 29 was prepared as follows:

Copper nitrate trihydrate (121.6 g) was dissolved in one liter of water,and 160 g of active alumina which was sufficiently finely divided bymeans of a ball mill with the removal of finer and coarser particles.With good stirring, an aqueous 10 wt.'% solution of sodium carbonate wasadded dropwise gradually over 30 minutes at room temperature to adjustthe pH of the solution to 7.5.

After continued stirring for an additional one hour, the solution wasallowed to stand overnight. The solution was then filtered, and thefiltrate was thoroughly washed with water, and dried at to C. With goodstirring in a stainless steel vessel, the powder obtained was carefullycalcined. The calcined product had a composition of 20 wt. CuO and 80wt. Al- O and the weight ratio of Cu/Al O after reduction with hydrogencorresponded to 0.20:1.

As a caking agent for the shaping of catalyst, 47.5 g of acid clay (theratio of acid clay/catalyst being 0.25 by weight) were added to g of thepowdery calcined product, and the mixture was well stirred and thenkneaded with water. The kneaded mixture was dried, and pulverized.Particles having a size of 9 to 12 mesh were collected.

The catalyst containing nickel or chromium oxide was prepared in thesame manner as in the preparation of the catalyst used in Example 24 byusing a mixed Table 5 Cu/solid Results of reaction acid ReactionControls Solid acids weight temp. Yield Con- Selec- 1 ratio (C) versiontivities 3 thorium oxide 0.34 260 7 78 g 9 4 acid clay 0.34 260 35 79 445 kaolin 0.34 260 13 71 18 6 bentonite 0.34 260 18 64 27 7 zinc borate0.20 250 17 87 30 8 zirconium 0.20 250 22 70 silicate aqueous solutionof copper nitrate and nickel nitrate or chromium nitrateinstead of theaqeuous solution of copper nitrate.

The process of the invention was performed in the same way as set forthin Example 1 using e-caprolactone (LON for short) or methyle-hydroxycaproate (MHC for short). The results obtained are given inzinc borate and zirconium silicate were heat-treated for 3 hours at 500550C. before the preparation of the catalysts.

EXAMPLES 37 TO 47 Titanium dioxide powder was suspended in a mixed Table4. 20

Table 4 Results of Catalyst composition ratio Reaction conditionsReaction Ex. Start- Caking Re- Space H NH H O/ Con- No. ing CatalystB-i-C/A C/B agent/ action velo- Starting Starting Starting Yield ver-Selecmatecomposition (atocatalyst temp. city material material materialsion tivity rial (A) (B) (C) (wt. mic (wt. (1/ (molar (molar (molarratio) ratio) ratio) (C) hr.l) ratio) ratio) ratio) 29 LON Alu Cu 0.20 00.25 250 360 23 4 20 67 84 80 mina 30 LON Cu Ni 0.34 0.05 0 260 368 20 820 80 98 82 31 MHC Cu Ni 0.34 0.05 0 260 368 20 8 20 76 97 78 32 LONSilica Cu 0.18 0 0.25 250 368 23 5 20 73 87 84 alu mina 33 MHC Cu Cr O0.34 0.05 0 260 368 20 8 20 74 96 77 34 LON Cu 0.34 0 O 260 368 20 8 2067 99 68 35 LON Cu Ni 0.34 0.05 0 260 368 20 8 20 80 98 82 36 LON SilicaCu 0.17 0 0 250 360 23 4 20 64 85 75 gel 1. Silica alumina in Examples32. 33 and 35 was 10 wt. SiO and 90 wt. 70 A1 0 2. Silica-alumina usedin Example 34 was 50 wt. SiO and 50 wt. 71' A1 0 3. In Example 29, acidclay was used, and in Example 32, diatomaceous earth was used as acaking agent.

CONTROLS 3 TO 8 aqueous solution of copper nitrate and a metal nitrateindicated in Table 6, and an aqueous alkali solution was added in thesame way as set forth in Example 1 to yield a catalyst. The process ofthe invention was performed using the catalyst so prepared ande-caprolactone as a starting material. The space velocity was 368liters/hr. liter. The molar ratios of hydrogen ammonia and water, basedon e-caprolactone, were 20:1, 8:1 and 20:1 respectively. The resultsobtained are shown in Table 6.

Table 6 The reaction time is the time from the initiation of thereaction Composition Metal of Catalyst Reac- Reac- Example oxide Cu/TiOThird tion tion No. added wt metal/cu temp. time Conver- Selecratioatomic (C) (hr.) Yield sion tivity ratio 37 MnO 0.33 0.053 260 9 12 6685 46 38 MnO 0.34 0.010 260 0 3 89 78 260 V 6 9 r 82 66 39 BaO 0.330.053 250 0 4 3 54 S0 51 40 8210 0.34 0.01 260 0 3 74 93 i 260 '30 36 5575 73 41 Co 0.33 0.053 250 0 3 64 63 42 Co 0.34 0.01 '260 0 3 74 94 7943 Fe O 0.34 0.053 250 0 3 34 85 40 44 ZnO 0.34 0.053 250 0 3 54 V 91 5945 MgO 0.34 0.053 250 0 3 31 72 43 46 A1 0 0.34 0.053 260 0 3 46 74 6247 CaO 0.34 260 0 3 52 85 61 17 EXAMPLES 48 TO 54 These Examples showthe results of experiments performed by using various startingmaterials.

A catalyst composed of titanium dioxide and copper and a catalystcomposed of titanium dioxide, copper and nickel were prepared in thesame way as set forth in Example 1 or Example 14 respectively. Usingvarious e-hydroxycaproic acid esters as starting materials, the processof the present invention was performed in the same way as set forth inExample 1. The results obtained are shown in Table 7.

18 EXAMPLES 61 TO 66 AND CONTROLS 13 TO 14 These Examples show therelation of the molar ratios of hydrogen and ammonia to the startingmaterial and the molar ratio of hydrogen to ammonia, with the results ofthe reaction.

A catalyst was prepared in the same way as in Example 14, in which theweight ratio of copper and nickel to titanium dioxide was 0.34:1 and theatomic ratio of nickel to copper was 0.05 2: l. The process of theinvention was performed using the catalyst and e-caprolactone (LON forshort) as a starting material, while the Table 7 Catalsyt Result ofcomposition Reaction condition r a ti z/ NH 11 Se- Example StartingCu+NiITiO Ni/Cu Reaction Space Starting Starting Starting YieldConverlec No. material temp. velocity material material material siontiv- (wt. ratio) atomic (1/hr.l) (molar (molar (molar ity ratio) ratio)ratio) ratio 48 MHC 0.34 0 250 368 8 20 71 86 82 49 EHC 250 368 67 88 7650 1P1-1C 260 368 64 88 73 51 NBHC 270 368 61 91 67 52 MHC 0.34 0.052260 368 78 94 83 53 EHC 260 368 73 93 79 54 NBHC 280 368 64 97 67 MHC:(Methyl e-hydroxycaproate) EHC: (Ethyl IPHC: (iso propyl NBHC: (n-butylEXAMPLES 55 TO AND CONTROLS 9 TO 12 These Examples were carried out attemperatures in the range of 180 to 360C.

molar ratios of hydrogen and ammonia to e-caprolactone were varied inseveral ways. The reaction temperature was 260C, and the space velocitywas 368 1iters/hr.liter. The results obtained are given in Table 9.

Table 9 Gas Composition Results of reaction Example H ILON NHJLON H /NHH O/LON Yield Conver- Selec- Nos. (molar (molar (molar (molar siontivity ratio) ratio) ratio) ratio) Example 61 26 2 13 20 76 97 78 62 235 4.6 20 84 98 86 63 20 8 2.5 20 85 98 87 64 15 13 1.2. 20 81 96 84 651O 18 0.56 20 67 90 66 5 23 0.22 20 41 75 55 Control 13 2 26 0.08 20 1557 27 14 0 28 0 20 0.5 46 1 Using a catalyst composed of titaniumdioxide, copper and nickel prepared in the same way as in Example 14 inwhich the weight ratio of copper and nickel to the titanium dioxide was0.34:1 and the atomic ratio of nickel to copper was 0.052:1 the processof the invention was performed using e-caprolactone as a startingmaterial. The molar ratios of hydrogen ammonia and water, based one-caprolactone, were 20:1, 8:1 and 20:1 respectively. The resultsobtained are given in Table 8.

Controls 13 and 14 were performed for comparative purposes. Control 14shows that' in the absence of hydrogen, e-caprolactam cannotsubstantially be formed.

EXAMPLES 67 TO 76 These Examples show the results of performing thereaction of the invention with varying molar ratios of water to thestarting material.

The process of the invention was performed in the 24. The results areshown in Table 10.

To determine the effect of water, the space velocities in Examples 67 to69 and those of Examples 70 to 75 were made equal respectively usingnitrogen gas instead of water.

by using e-caprolactone (LON for short) as the starting material and acatalyst prepared in the same way as set forth in Example 14 or 1 fromtitanium dioxide and copper, or from titanium dioxide, copper andnickel.

The results are given in Table 12..

The space time yield of e-caprolactam is the number of moles of e-caprolactam yielded for 1 hour per liter of the catalyst.

Titanium dioxide used in Examples 83 to 85 con- Table 1 Result ofCatalyst composition Reaction condition reaction Cu+Ni+ Re- HJ Nl-l l HO! N Con- Ex. Starting Cr O Ni/Cu Cr/C u action Space Starting StartingStarting Starting Yield ver- Selec- No. Material TiO (atomic (atomictemp. velocity material material material material sion tivity (wt.ratio) ratio) (C) (l/hr.l) (molar (molar (molar (molar ratio) (ratio)ratio) ratio) 67 LON 0.20 0.05 0 260 391 23 8 20 0 83 97 85 68 O 391 238 1O 1O 77 98 79 69 0 391 23 8 0 20 63 99 64 70 MHC 0.34 0 0.05 260 36820 8 2O 0 82 96 85 71 20 8 0 20 63 91 69 72 LON 0.34 0.052 0 260 368 208 0 20 65 99 66 73 368 20 8 l0 79 99 80 74 368 20 8 5 83 98 85 75 368 820 0 85 98 87 76 It 235 20 8 0 7s 90 87 EXAMPLES 77 TO 82 These Examplesshow the results of the reaction performed at varying space velocities.

The process of the invention was performed using.

-e-caprolactone as the starting material and a catalyst sisted of 4% byweight of particles having a size less than 28 90% by weight ofparticles having a size of 28 to 35p., and 6% by weight of particleshaving a size of more than 35 1.. This particle size distribution wasdetermined by the sedimentation method at 24C. using a Kelly tube and asuspension of 37 g of titanium dioxide per liter of an aqueous solutionof copper nitrate having a concentration of 0.2 mol/liter, and using theStokes equation.

Titanium dioxide used in Examples 86 to 88 contained 90% by weight ofparticles having a size of 0.1 to 1]..- The particle size distributionwas determined as follows: The sedimentation method was employed at 24C.using a Kelly tube and a suspension containing 37 g of titanium dioxideper liter of an aqueous solution of Results of Reaction EXAMPLES 83 TO88 These Examples illustrate the comparison of the activities ofcatalysts prepared by using titanium dioxides of different particle sizedistributions.

The process of the present invention was performed copper nitrate havinga concentration of 0.2 mol/literr After a lapse of 1 hour, titaniumdioxide particles which did not at all sediment were separated. Theparticle size of such titanium dioxide particles was measured by thecentrifugal sedimentation method at a concentration of titanium dioxideof 2% by weight in water.

Table 12 Catalyst composition Reaction condition Results of reaction Ex.Size distribution of Cu+Ni/ Reac- Space Con- Space time No. titaniumdioxide TiO Ni/Cu tion velo- Hg/LON NHJLON HgO/LON Yield ver Selecyieldof used (wt. (atomic temp. city (molar (molar (molar sion tivity caproratio) ratio) (C) (l/ ratio) ratio) ratio) lactam hr.l) (mol/Lhr) lessthan 28p. 4 wt% 83 28 35p. wt% 0.34 0 250 382 22 8 20 88 99 89 0.30

more than 6 wt% Table 12 -Continued Catalyst composition Reactioncondition Results of reaction Ex. size distribution of Cu+Nil Reac-Space Con- Space time No. titanium dioxide TiO, Ni/Cu tion velo- HJLONNH /LON H O/LON Yield ver- Selecyield of used (wt. (atomic tem city(molar (molar (molar sion tivity e-caproratio) ratio) (l ratio) ratio)ratio) lactam hr.l) (mol/l.hr)

84 270 500 22 8 20 84 98 86 0.35 85 0.20 0.05 260 368 20 8 20 83 97 850.28 86 0.1 1.0g 90 Wt% 0.34 O 260 382 22 8 20 56 65 86 0.19 87 270 38222 8 20 67 80 84 0.22 88 0.20 250 382 22 8 20 52 61 85 0.17

It is seen from the comparison of Examples 83 and In the preparation ofthe catalyst used in Example 94,

86, Examples 84 and 87, and Examples 85 and 88 that the use of titaniumdioxide having a suitable particle size distribution leads to theproduction of effective catalysts desired in the process of the presentinvention.

EXAMPLES 89 TO 95 These Examples show the results of performing theprocess of the present invention using catalysts which consist oftitanium dioxide and copper in the same way as in Example 1 except thatsome other alkali aqueous solutions were used instead of the aqueoussolution of cupric chloride was used instead of copper nitrate, and inthe preparation of the catalyst used in Example 95, cupric acetate wasused instead of copper nitrate. In both of these Examples, an aqueoussolution of sodium carbonate was used as the alkali aqueous solution.

In the catalysts used in Examples 94 and 95, the weight ratio of copperto titanium dioxide was 0.34:1.

The process of the invention was performed in the same way as mentionedin Example 1 using the catalysts prepared above and e-caprolactone asthe starting material. The results obtained are shown in Table l2(a).

Table l2(a) Reaction conditions Results of reaction Reaction Space HJLONNH -,/LON H O/LON Extemperavelocity Yield Conver- Selecample ture (molar(molar (molar sion tivity No. (C) (l/hr.l) ratio) ratio) ratio) 89 260368 23 5 20 83 98 85 90 260 368 23 5 20 8 l 97 83 9 l 260 368 20 8 20 7898 79 92 260 368 20 8 20 79 98 8 l 93 260 368 20 8 20 72 95 76 94 260368 20 5 20 84 96 77 95 260 368 20 5 20 73 97 75 sodium carbonate andsome copper salts instead of copper nitrate.

The catalyst used in Examples 89 to 93 was prepared by suspending 200 gof powders of titanium dioxide in 3 liters of an aqueous solutioncontaining 260 g (1.08 moles) of copper nitrate trihydrate, and addingan alkali aqueous solution dropwise to the suspension at to C. withstirring, followed by the same treatments as set forth in Example 1.

In the preparation of the catalyst used in Example 89, a mixed aqueoussolution of sodium carbonate and so dium hydroxide (containing 0.5 molof sodium carbonate and 1.0 mole of sodium hydroxide per liter) was usedas the aqueous alkali solution to adjust the pH to 9.

In the preparation of the catalyst used in Example 90, an aqueoussolution of sodium hydroxide having a concentration of 2 moles/liter wasused as the alkali aqueous solution, to adjust the pH to 9.

In the preparation of the catalyst used in Example 9 l, 1 liter of anaqueous solution containing 2.2 moles of ammonia was used as the alkaliaqueous solution.

In the preparation of the catalyst used in Example 92, 1 liter of anaqueous solution containing 2.2 moles of ammonium carbonate was used asthe alkali aqueous solution.

In the preparation of the catalyst used in Example 93, 1 liter of anaqueous solution containing 2.2 moles of ammonium bicarbonate was used.

EXAMPLES 96 TO These Examples show the results of performing the processof the invention using catalysts prepared by some different methods.

The catalyst used in Examples 96 to 101 was prepared by suspending 250 gof the'powders of basic copper carbonate obtained by mixing an aqueoussolution of copper nitrate with an equivalent amount of an aqueoussolution of sodium carbonate, and 200 g of titanium dioxide powder in 2liters of water, stirring the suspension for 30 minutes, filtering it,drying the filtrate, calcining it with stirring, kneading the calcinedproduct with water, drying the kneaded mixture, pulverizing it, andcollecting particles having a size of 9 to 12 mesh. The weight of copperbased on titanium dioxide was about 08:1.

The catalyst used in Examples 102 to 104 was prepared by suspending 1 15g of copper oxide powder obtained by thermal decomposition of basiccopper carbonate powder with good stirring, and g of the of titaniumdioxide powder in 1.5 liters of water, stirring the suspension for 30minutes, filtering the suspension, kneading the filtrate well, dryingit, pulverizing it, and collecting particles having a size of 9 to 12mesh. The weight ratio of copper to titanium dioxide was 0.78:1.

The catalyst used in Examples 105 and 106 was prepared by suspending 200g of titanium dioxide powder in 2 liters of an aqueous solution ofcopper nitrate having a concentration of 2 moles/liters, stirring thesuspension at 50C. for 1 hour, allowing it to stand overnight at 50C.,suction filtering it, drying it completely free of water, calcining theresulting powder with good stirring to form a powder consisting oftitanium dioxide and copper oxide, kneading the powder witli'water,drying the kneaded mixture, pulverizing it, andcollecting particleshaving a size of 9 to 12 mesh.

The catalyst used in Examples 107 to 110 was prepared by mixing copperhydroxide obtained from copper nitrate and ammonia water with titaniumdioxide in water, filtering the mixture, drying the filtrate, calciningit, and then shaping it.

The process of the invention was performed in the same way as set forthin Example 1 using the catalyst so prepared and e-caprolactone as astarting material. The results are shown in Table 13.

Examples 96 through 101, Examples 102 through 104, Examples 105 and 106,and Examples 107 through 110 were each performed successively using thesame catalyst as specified above with respect to each group of Examples.

Table 13 From the comparison of Example 1 l l with Example 6 in whichthe catalyst was wet shaped, it is seen that there is substantiallyno'difference between them.

EXAMPLE 1 13 This Example shows the activating treatment of the catalystthe activity of which was reduced through use in the practice of theprocess of the invention for relatively long periods of time.

A catalyst comprising titanium oxide and copper in Reaction conditionsResults of reaction Ex- Reac- Reaction Space H2/CON NH LON H O/LON'Yield Conver-' Selecample tion temvelosion' tivity (hr.) (C) (l/hr.l)ratio) ratio) ratio) EXAMPLES 111 TO 112 Table 15 These Examples showthe results of performing the 4 present invention using a catalystshaped in tablet form 5 Reaction time Yield which was prepared in thesame way as set forth in Ex- (hours) ample 84 97 87 A powder consistingof titanium dioxide and copper I i 67 85 79 oxide was prepared in thesame way as set forth in Ex- 0 ample l, in which the weight ratio ofcopper to titanium dioxide was 0.34:1. The powder was formed intotablets having a diameter of 6 mm and a thickness of 1.5 mm, at apressure of about 800 Kglcm Using cc (72 g) of the resulting catalystand e-caprolactone as a starting material, the process of the inventionwas performed in the same way as set forth in Example 1. The results areshown in Table 14.

Table 14 Reaction Conditions 3 Results of Reaction Example Temp. SpacePl /LON NH /LON H O/LON Yield Conver- Selec- No velocity (molar (molar(molar sion tivity (C.) (l/hr.l) ratio) ratio) ratio) (7t gen gas (bothbeing calculated as gases under normal conditions) was introduced. Withoccasional control of the flow rate of air, the catalyst was oxidizedfor 1 hour at 350 550C.

steam through a water evaporating tube were provided, and at the lowerend, an outlet opening for the reacted mixed gas was provided. Thereacted mixed gas was introduced from a water cooler to a receiver, andpassed After the oxidizing treatment, nitrogen gas was intro- 5 througha trap with dry ice-methanol. At positions 50 duced from the upper endof the preheating pi e t mm from the lower end of the reactor and 450 mmpurge the system thorou hl Th catalyst wa th n from the lower end of thereactor perforated plates duced with hydrogen under substantially thesame conwere Provided, ahd'eemmie Rasehig rings were Packed ditions asused initially. Using the activated catalyst, to a height of 50 mm fromthe Perforated Plate at the the reaction was performed under the sameconditions lower P on p of the rings 500 CC g) of e as given above. Theproduct yielded for 3 hours after catalyst were packed, and on thecatalyst ceramic Rasthe passage of 3 hours from the initiation of thereacchig rings were packed so that the distance between the hon wasanalyzed The Conversion of e'eaprolaetone perforated plate at the upperpart and the surfaces of was 95 the yield of e-caprolactam was 81 andthe h rings was 50 selectivity of e-caprolactam was 85 This indicated 13o the other hand, Ceramic Raschig rings were the regeheratleh 0f thecatalyst aehvltypacked into a portion from the upper perforated plate toa point 90 mm from the upper end of the reactor to EXAMPLE 1 14 form apreheating layer. Thermometers were placed at This Example shows theactivating treatment of a catabout the center of the preheating layerand the Cataalyst prepared from basic copper carbonate and titalystlayer. A band heater was wound around the reacnium dioxide. tor, and anasbestos band was wound on top of it.

The catalyst the activity of which W .reduced Nitrogen gas wasintroduced from the gas inlet openthrough use in Examples 96 to 101 wastreated for 1 ing of the reactor to purge the reactor thoroughly, andhour and 30 minutes with a gaseous mixture of air and then a gaseousmixture of 0054125 liter/min of Q f gas at 40045000 Wlth the replacementof drogen gas and 3.0 liters/min. of nitrogen gas was introthe msldeatmosphere of the reactor by mtrogen s duced. The catalyst was reducedwith hydrogen for 7 the temperature was decreased. The catalyst was reh1 SOLZSOOC M l h duced with hydrogen at a temperature below 250C. Oursat w 1e pFopery comm mg 6 Using e-caprolactone as a starting material,the process flow rate of hYdrfJgen gas agamst temperature use of theinvention was performed at 260C. at a Space due to the generation ofheat. Hydrogen gas was further locity of 368 liters/hourliter for atotal of 9 hours. The Passed at a flow rate of liters P minute at 250Cmolar ratios of hydrogen, ammonia and water to ecafor 3 hours. Thetemperatures of the preheating layer prolactone were respectively 23:1,5:1 and 20:1. The and the catalyst layer were respectively set at 270C.following results were obtained. d 260C Yield(%) Conversion(%)Selectivity(%) For the first 0-3 hours: 75 93 81 From 3 to 6 hours: 7691 83 From 6 to 9 hours: 75 92 82 Before the activating of the catalyst,the yield of e-cap- Hydrogen and ammonia were introduced from therolactam was 32 It can be seen from the comparison ga inlet o ening at aflow rate of 72 liters/hr and 29 liof the results of Example 98 for 6 to9 hours with those. /h respectively, d water was f d to h reactor hlabove t the activating treatment gave at a rate of 58 g/hr through thewater evaporating tube. blmy to the catalytlc actwlty' e-Caprolactonewas passed at a rate of 18.3 g/hr, and

' a continuous reaction was performed. The results ob- EXAMPLE 113tained are given in Table 16.

Example 115 to 120 show the results of the reaction Table 16 for a longtime be repeating the activation of the catalyst.

The Catalyst used in Examples 1 15 to 120 was pre Reaction time Yield czli si rl electivity pared as follows: (hours) (70) Using 7 liters of anaqueous solution containing 688 g of copper nitrate trihydrate and 54 gof nickel nitrate 6 84 96 87 hexahydrate, 550 g of titanium dioxide(mostly having 3; E 3; g:

a particle diameter in the range of 28 to 35p. in the 48 74 89 83aqueous solution), and 1.0 mol/liter of sodium carbonate? powder-sCOnSi-sting of titanium Flioxide copper The reaction time in the tablerefers to the time that oxide and n1ckel oxide were prepared in the sameway h d the as set forth in Example 1. The powders were kneaded elapsedsmce the lmtlauon 0ft e ractlon an with water, dried, and pulverized,and particles havin $111115 0f the aCtlOfl are those obta ned for thepast 6 a particle size of 7 to 12 mesh were collected. hours from thehme lhdleated- (Thls 1 pply to The reactor used consisted of a verticalquartz tube [316$ 17 to 21 appearing later in the Speelfieahoh-) havingan inner diameter of 60 mm and a length of 11 10 mm. At a position 60 mmfrom the upper end of the tube an opening for adding of the material, agas inlet opening, and an inlet opening for introduction of EXAMPLE 1 16After the end of the operation in Example 115, the inside of the reactorwas replaced with nitrogen gas,

Table 17 Results of the reaction Reaction time Yield ConversionSelectivity EXAMPLE 1 17 After the end of Example 1 16, water vapor (ata flow rate of 110 g/hr. fed through the water vaporization tube) waspassed at 250C. for 3 hours, and then a gaseous mixture of air andnitrogen gas was passed for 3 hours at less than 300C. The reduction ofthe catalyst with hydrogen was performed for 4 hours at less than 250C.After the activating treatment, the reaction was performed under thesame conditions as set forth in Example 1 15. The results obtained aregiven in Table 18. a

Table 18 Results of the reaction Reaction time Yield ConversionSelectivity EXAMPLE 1 18 After the end of Example 117, the activation ofthe catalyst was performed in the same way as in Example 17 at 300-350C.Using the activated catalyst, the reaction was performed continuouslyunder the same conditions as in Example 115. The results obtained aregiven in Table 19.

Table 19 Results of the reaction Reaction time Yield ConversionSelectivity (hours) EXAMPLE 1 19 After the end of Example 1 18, thecatalyst was activated in the same way as set forth in Example 118.Using the activated catalyst, the reaction was performed under the sameconditions as set forth in Example 1 15. The results are shown in Table20.

EXAMPLE 120 After the end of Example 1 19, the catalyst was withdrawnfrom the reactor, and washed with about 5 liters of water at 80C.,followed by drying to be free of water. The catalyst was then carefullyheated with stirring in a stainless steel vessel. The catalyst sotreated was sieved, and particles having a particle size of 7 to 12 meshwere collected. Those particles which passed through a 12-mesh sievewere kneaded with water, and the kneaded mixture was dried and thenpulverized. Particles having a particle size of 7 to 12 mesh werecollected.

370 cc (295 g) of the catalyst so obtained were reduced with hydrogen inthe same way as set forth in Example 1 15, and with the catalyst soobtained, the reac tion was performed at 260C. using 14 g/hre-caprolactone, 55 liters/hr hydrogen, 22 liters/hr ammonia and 44 g/hrwater. The results obtained are given in Table The reaction wasperformed for a total of 444 hours from Example with the activating ofthe catalyst carried out 5 times. The results show that the activatingtreatments did not adversely affect the catalyst, but rather gave acatalyst having a stable catalytic activity for prolonged periods oftime.

CONTROL l5 Molded Adkins type copper chromium catalyst (composed of44-46 CuO, 4244% Cr O and 45% MnO was pulverized, and particles having 9to 12 mesh were collected. Using the catalyst so obtained, the reactionwas performed for a total of 24 hours at 260C. and a space velocity of368 liters/hr.liter. The

What we claim is:

l. A process for producing e-caprolactam which comprises contacting atleast one compound selected from e-caprolactone and C -C lower alkylesters of molar ratios of hydrogen, ammonia and water to e-ca- 5E'hydroxycaproic acid with hydrogen f amngonia in prolactone were 20:1,8:1, and 20:1 respectively. .The the vapor phase at a t m 200 to 320with results obtained are given in Table 22. a sohd catalyst Gongs/[mgessenuany of A. at least one oxide selected from the group conslst-Table 22 ing of titanium dioxide, alumina, alumina-silica and 10 silica,R l fth B. metallic copper, and Reaction time Yield gg z g e C. at leastone component selected from the group (hours) consisting of metallicnickel and chromium sesqui- 0 3 60 88 68 oxide the sum of the amounts ofthe metallic cop- 3 6 58 86 67 per (B), the component (C) being 0 to 200parts 6- 12 51 81 63 by weight. 24 47 72 64 2. The process of claim 1,wherein said solid catalyst contains 100 parts by weight of said oxideand 0.5 to After the 24-hour reaction, the catalyst was activated 200parts by weight of metallic copper. in the Same way as Set forth inExampl 1 ng the 3. The process of claim 1, wherein said solid catalystactivated catalyst, the reaction was performed under comprises particlesor agglomerated particles of said the same conditions. At the end of6-hour reaction, the oxide h vin a particle size of 5 to 100 microns,and yield of e-caprolactam was 55 the Con ersion Of metallic copperdeposited on the surfaces of said partie-caprolactone was 83%, and theselectivity of e-caprocles. lacta W38 The results Show a the Adkins 4. Aprocess of claim 1, wherein said solid catalyst copper Chromium catalystnnot e ffi i n ly aCticomprises anatase type titanium dioxide andmetallic vated. copper.

5. The process of claim 1, wherein said solid catalyst CONTROLS 16 to 21is prepared by dispersing said oxide in an aqueous solu- These controlsshow the results of performing the ref a PP F compound or an aqueousSuspension action using a catalyst composed of copper and ch calclnmgthe mixture at 200600C., and reducing the mium oxide free of titaniumdioxide, alumina, aluminamixture until at least the Surface of 531d ppsilica or silica gel. pound is substantially converted to metalliccopper.

The catalyst used was prepared as follows; 6. The process of claim 1,wherem said solid catalyst One mole/liter of an aqueous solution ofsodium car- Consists of bonate was added dropwise gradually withstirring to 4 100 Parts y Weight Of at least one Oxide Selected litersof a mixed aqueous solution containing 435 g of fttfm the g p Consistingof titanium dioxide, copper nitrate trihydrate and 72 g of chromiumnitrate mma, alumina'silica and Silica, nonahydrate, to adjust the pH to8.5. The solution was B. metalhc pp and allowed to Stand for one day,and the precipitate was 40 C. a component selected from metallic nickel,chrowashed with water, followed by drying at 90110C. mium sesquioxideand mixtures thereof, the sum of The product was carefully decomposed byheat with the amounts of the metallic pp and metalgood stirring in astainless steel vessel. In the calcined he nickel, Chromium sesquioxideor mixture product, the ratio of Cr to Cu was 01:1. The powdery thereofbeing 05 to 200 Parts y Weight, and calcined product was kneaded withwater, and the the atomic ratio of Component as nickel, chr0- kneadedmixture was dried, and pulverized. Particles mium or mixture thereof, tometallic pp having a particle size of 9 to 12 mesh were collected, being0.001 to 1:1. and then reduced with ahydrogen-containing gas in the 7.The process of claim 1, wherein at least one of same way as set forth inExample 1. Similarly, catalysts 5O e-caprolactone or C C alkyl esters ofe-hydroxycacontaining copper and chromium oxide in varying proproicacid, hydrogen, ammonia are contacted with said portions were prepared.The reaction was performed solid catalyst in the vapor phase togetherwith water. using each of the catalysts so prepared. The results ob- 8.The process of claim 1, wherein per mole of e-catained are shown inTable 23. prolactone or said esters of e-hydroxycaproic acid,

Table 23 Selectivity Yield of Cr/Cu Reaction Space HZ/LON NHQILONHQOILON Conversion of e-caproe-capro- Example (atomic Starting temp.velocity (molar (molar (molar lactam lactam No. ratio) material (C)(l/hr.l) ratio) ratio) ratio) l6 0.] LON 250 368 I8 10 2O 85 64 17 0,1LON 260 368 20 8 2O 91 57 52 18 0.1 MHC 260 368 20 8 20 92 59 51 19 0.2LON 250 368 20 8 20 62 58 36 20 0.2 LON 260 368 20 8 20 74 46 34 21 0.5LON 260 368 20 8 20 71 41 30 of the copper compound, precipitating thecopper compound when the aqueous solution of copper compound is used,separating a mixture of solid copper compound and the oxide from theaqueous medium,

a. 5 to moles of hydrogen, b. 1 to 50 moles of ammonia, and c. O to 50moles of water are used.

UNITED STATES PATENT OFFICE fiERTIFICATE OF CORRECTION Patent No.3,888,845 Dated June 10, 1975 Inventor s) FUJITA ET AL It is certifiedthat error appears 'in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

In the claims, correct Claim 5 as follows:

Claim 5, line 3, after "suspension" insert of the copper compound,precipitating the copper compound when the aqueous solution of thecopper compound is used, separating a mixture of solid copper compoundand the oxide from the aqueous medium,

Signed and Scaled this thirtieth Day of September 1975 [SEAL] RUTH C.MnSON c. MARSHALL DANN AIM-"mg Office (mnmissimwr nj'lau'nrs andTradcmurks

1. A PROCESS FOR PRODUCING $-CAPROLACTAM WHICH COMPRISES CONTACTING ATLEAST ONE COMPOUND SELECTED FROM $CAPROLACTONE AND C1=C4 LOWER ALKYLESTERS OF $HYDROXYCAPROIC ACID WITH HYDROGEN AND AMMONIA IN THE VAPORPHASE AT A TEMPERATURE OF 200* TO 320:C, WIT
 2. The process of claim 1,wherein said solid catalyst contains 100 parts by weight of said oxideand 0.5 to 200 parts by weight of metallic copper.
 3. The process ofclaim 1, wherein said solid catalyst comprises particles or agglomeratedparticles of said oxide having a particle size of 5 to 100 microns, andmetallic copper deposited on the surfaces of said particles.
 4. Aprocess of claim 1, wherein said solid catalyst comprises anatase typetitanium dioxide and metallic copper.
 5. The process of claim 1, whereinsaid solid catalyst is prepared by dispersing said oxide in an aqueoussolution of a copper compound or an aqueous suspension of the coppercompound, precipitating the copper compound when the aqueous solution ofcopper compound is used, separating a mixture of solid copper compoundand the oxide from the aqueous medium, calcining the mixture at200*-600*C., and reducing the mixture until at least the surface of saidcopper compound is substantially converted to metallic copper.
 6. Theprocess of claim 1, wherein said solid catalyst consists of A. 100 partsby weight of at least one oxide selected from the group consisting oftitanium dioxide, alumina, alumina-silica and silica, B. metalliccopper, and C. a component selected from metallic nickel, chromiumsesquioxide and mixtures thereof, the sum of the amounts of the metalliccopper (B) and metallic nickel, chromium sesquioxide or mixture thereof(C) being 0.5 to 200 parts by weight, and the atomic ratio of component(C), as nickel, chromium or mixture thereof, to metallic copper (B)being 0.001 to 1:1.
 7. The process of claim 1, wherein at least one ofepsilon -caprolactone or C1 - C4 alkyl esters of epsilon -hydroxycaproicacid, hydrogen, ammonia are contacted with said solid catalyst in thevapor phase together with water.
 8. The process of claim 1, wherein permole of epsilon -caprolactone or said esters of epsilon -hydroxycaproicacid, a. 5 to 70 moles of hydrogen, b. 1 to 50 moles of ammonia, and c.0 to 50 moles of water are used.